Certain flat panel displays such as liquid crystal displays and the like do not produce light themselves. Illumination (ambient light or a special light source) is therefore needed in order to produce visible images for such a display. A backlight is a form of illumination used in displays including liquid crystal displays (LCDs), active matrix liquid crystal displays (AMLCDs) or the like. Light source for a backlight may include white or colored light-emitting diodes (LEDs).
Displays used in some applications may be required to be compatible with night vision imaging systems (NVIS). For instance, certain avionics and/or ground vehicle displays not only need to be visible to unaided eyes, but also need to be compatible with night vision equipment (e.g., night vision goggles) without adversely affecting the operation of the night vision equipment. Traditional NVIS compatible LED backlights are typically single mode in operation with all of the LEDs being filtered by complex and expensive thin film filters. These single mode backlights are limited by luminance loss in day time operation as well as backlight dimming stability at the low end of the luminance range.
NVIS compatible dual mode backlights brought improvements addressing these specific issues, but most of these early dual mode backlights were encumbered with their own shortcomings. Many were difficult to build and produce or equally expensive relative to their single mode counterparts. Later dual mode variants improved upon cost, complexity, and producibility, but still encountered limitations, such as reliance upon specialized LED packaging styles such as reverse-mount emitter types which were limited in supplier base and lacking sufficiently tight specification control for color and luminance binning. Therein lies a need for a night vision compatible LED backlight that overcomes these shortcomings.